In some types of liquid handling, for instance transport of large volumes of lightly contaminated water such as surface water, a submersible pump in the form of an axial pump present a number of advantages. Axial pumps are arranged lowered into column pipes and are typically electrically driven wherein the power supply to the pump is effected via one or more cables that extend down to the pump via the inside of the column pipe.
Thus, the pump is normally intended to be placed in a column pipe that is partly lowered into the pumped media. Before start up the axial pump is lowered into the column pipe until it stands on a bottom flange in the column pipe and thereby seals tightly against the column pipe. Consequently the pump is entirely or partly submersed into the media when it has reached its operational position. During operation the column pipe also work as an outlet pipe for the pumped liquid. Before service the pump is hoisted and removed from the column pipe.
Lowering as well as hoisting of the pump is normally performed by means of a winch device such as a fixed or mobile crane comprising a strong chain having a hook in the lower end thereof. The hook is configured to hitch a lifting handle of the pump. Axial/vertical transportation of the pump through the column pipe is allowed when the hook is in engagement with the lifting handle.
When the axial pump occupies the operational position it is necessary according to prior art to unhook the hook from the lifting handle and entirely remove the chain from the column pipe. This is done in order to avoid that the strong liquid currents that always arise in the column pipe during the operation of the axial pump would bring the chain in violent motions. Such an uncontrolled rotating oscillatory motion of the chain would unavoidably damage the electric cables that extend from the pump and up inside the column pipe to the upper end thereof. It shall be mentioned that the electric cables are attached to and axially displaceable along a stretched wire extending from the pump and to the upper end of the column pipe. If the electric cables would not be attached to the wire they would be brought in a rotating oscillatory motion and be damaged against the inner surface of the column pipe.
However, the abovementioned known methods including removal of the chain before operating the pump suffer from at least one considerable drawback. More precisely, there is no easy way of hitch the previously unhooked hook of the chain on the lifting handle of the pump before a coming hoisting of the pump. In this context, an arduous and time consuming method to hitch the hook on the lifting handle is to lower the open hook to an appropriate vertical level and thereafter try to hitch the open hook in the lifting handle of the pump. In an alternative method a guide wire may be used that extend from the ground level (upper end of the column pipe), under the lifting handle of the pump and back to ground level. Before hoisting of the pump the guide wire can be connected to the hook of the chain and thereafter the hook can be lowered and the hook may fairly well be controlled to a right position for hitching the lifting handle.